1. Field of the Invention
This invention relates to a variable capacitor of the type in which the capacitance is varied with the rotation of a shaft.
2. Technical Considerations and Prior Art
A typical variable capacitor comprises alternately disposed stator plates and rotor plates between which a dielectric is positioned.
In such variable capacitors, it is important that the distance between each stator plate and the rotor plate facing it is accurately fixed to obtain the predetermined capacitance characteristics. Consequently the instances between the adjacent stator plate as well as the adjacent rotor plates must be accurately held at the predetermined value. This is done by a spacer member, such as a washer which is disposed therebetween. However, washers, when punched out of a metal sheet have errors which range between plus and minus 0.01 percent in thickness from the desired value. Moreover, burrs, formed during the punch-out process, occur on the inner and outer edges.
In the conventional variable capacitors, the rotor plates are made of a comparatively soft and easy-to-fabricate material, such as aluminum, and are provided with a number of slits. These slits permit deformation, or bending, of the rotor to adjust the capacitance of a particular section at a given rotational angle.
Adjustments made in this manner are tedious and time consuming, moreover, the plates thus deformed are liable to return to the original shape with the lapse of time thereby changing the capacitance characteristics.
Accordingly, when the punched-out type washers are used, they must be lapped to the predetermined thickness. This results not only with increased manufacturing cost but also in a loss in yield caused by "over-lapping" to thinner thicknesses than required.